Circuit breakers, line switches, disconnect switches and capacitor switches are well known components of electric transmission and distribution systems. Within these devices, spring-driven acceleration mechanisms have been used to accelerate penetrating contactors to sufficient velocity to extinguish an arcing contact occurring across a contactor gap within the switch without experiencing an undesirable restrike, which could otherwise cause disturbances on the electric power system. This typically requires extinguishing the arc after one-half cycle, which prevents a restrike from occurring after the initial arc break that occurs at the first half-cycle zero voltage crossing after initial separation of the contacts. For this type of device, it is helpful to house the penetrating contactor within an insulator that forms a sealed container filled with a dielectric gas such as sulfur hexafluoride (SF6), which is directed into the contactor gap by a nozzle to help extinguish the arc. Extinguishing the arc in this manner, which is specifically designed to effectively absorb the arc energy, reduces the contactor gap separation required to extinguish the arc from what would be required to extinguish the arc in another environment such as air. The basic design challenge for this type of device involves engineering an acceleration mechanism that obtains the desired contractor velocity quickly enough to extinguish the arc without experiencing an undesired restrike within acceptable weight, size and cost constraints. An example of this type of device are described in U.S. Pat. No. 8,063,333, which is incorporated herein by reference.
A great deal of attention has been paid to the design of the contactors and the nozzle of this type of switch to prevent potentially damaging restrikes from occurring between the contactors, which allows the contactors to withstand extremely high electric fields. A potential drawback can occur when the electric field between the contactors becomes so high that a flashover occurs between other components of the switch. For example, damaging flashovers have been known occur between the casings housing the contactors even though the casings are physically further apart than the contactors themselves.
Accordingly, there is an ongoing need for cost high voltage effective electric power switch design that avoid flashovers from occurring between internal switch components other than the penetrating contactors.